DETECTION OF CANCER MICROMETASTASES IN LYMPH-NODES BY REVERSE TRANSCRIPTASE-POLYMERASE CHAIN-REACTION

There are few DNA-based studies that detect cancer micrometastases in lymph nodes. We have assayed for the specific detection of carcinoembr yonic antigen (CEA)-expressing carcinoma cells in the lymph nodes of p atients with gastrointestinal or breast carcinomas. A CEA-specific nes ted reverse transcriptase (RT)-PCR assay was optimized using limiting dilutions of a CEA-positive cancer cell line mixed with normal lymphoc ytes. The expression of CEA mRNA was studied in 100 carcinoma tissues, 75 normal mucosal tissues, and 15 lymph nodes from patients with chol elithiasis. Each of 117 lymph nodes from 13 patients with carcinoma wa s divided into two pieces: one was used for histological examination a nd the other for RT-PCR, and the results were compared. The sensitivit y ratio was one CEA-expressing cancer cell detected in 1 x 10(5) norma l lymphocytes. Ad carcinoma tissues and normal mucosal tissues express ed CEA mRNA, while no amplification was detected in any control lymph nodes. Thirty of 117 Lymph nodes were histologically involved by carci noma cells, and all of these yielded the expected product by RT-PCR. O f the remaining 87 histologically negative nodes, CEA mRNA was detecte d in 47 lymph nodes by RT-PCR. The positive rate increased from 26% by histological examination to 66% by RT-PCR. The assay by CEA-specific nested RT-PCR is not only sensitive but widely applicable for the dete ction of cancer micrometastases in lymph nodes. This method mag lead t o an earlier diagnosis and treatment of patients with subclinical lymp h node metastasis.